Method of fabricating a hollow turbine blade having an insert therein

ABSTRACT

A hollow cooled gas turbine blade is made by forming an insert with a hollow airfoil and a hollow root portion and with lateral cooling air passages extending through the wall of the airfoil and positioning the insert in a hollow main blade having an airfoil portion and a notch in the root to receive the root portion of the insert with both root portions having aligned serrations on opposite surfaces for supporting the blade and the insert in a turbine disk.

United States Patent 1 1 111 3,747,182 Hayes 1 1 July 24, 1973 [54] METHOD OF FABRICATING A HOLLOW 2,848,192 8/1958 Hayes 416/90 TURBINE BLADE HAVING AN INSERT 3,446,480 5/1969 Emmerson et al.... 416/90 THEREIN 3,635,587 6/1970 Giesman et al. 416/97 [75] Inventor: Charles W. Hayes, East Hartford, FOREIGN PATENTS OR APPLICATIONS Conn. 708,721 5/1965 Canada 29 1568 H 723,392 2/1955 Great Britain.v 29/1568 H Asslgooor United Aircraft C p East 726,909 3/1955 Great Britain 29/1568 H Hartford, Conn. 833,770 4/1960 Great Britain 416/97 [221 Filed: Feb. 1972 Primary Examiner-Charles W. Lanham [21] Appl. No.: 227,838 Assistant Examiner-D. C. Reiley, lll

Related US. Application Data Attorneycharles warren [62] 1331;56:192-156. No. 35,361, May 7, 1970, Pat. No. ABSTRACT A hollow cooled gas turbine blade is made by forming 521 U.S. c1. 29/156.8 it an insert with a hollow airfoil and a hollow root portion 51' Int. Cl im 15/02, 823p 15/04 and with lateral cooling air passages extending through 53 Field of Search 41 90 92 9 97 the wall of the airfoil and positioning the insert in a hol- 416/2]7 219; 29/1563 H low main blade having an airfoil portion and a notch in the root to receive the root portion of the insert with 56 R f ren Ci both root portions having aligned serrations on oppo- UNITED STATES PATENTS site surfaces for supporting the blade and the insert in 2,559,131 7 1951 Oestrich et al. 4l6/92 a turbine 2,780,435 2/l957 Jackson 4l6/90 3 Claims, 9 Drawing Figures METHOD OF FABRICATING A HOLLOW TURBINE BLADE HAVING AN INSERT TIIEREIN This is a division of application Ser. No. 35,361 filed May 7, 1970, US. Pat. No. 3,697,192.

BACKGROUND OF THE DISCLOSURE For cooling gas turbine blades in high performance engines, it is desirable to direct cooling air onto selected areas of the inner wall surface of a hollow turbine blade, as for example the wall surface adjacent to the leading edge of the blade which is subjected to the most intense heat within the turbine. If an inner sleeve is positioned within the hollow blade for directing the flow of cooling air, the formation of transverse fluid directing holes in the inner sleeve is a serious machining problem. The inner sleeve, functioning primarily as an airflow controlling device, should desirably be as light as possible and still withstand the centrifugal loading on the insert when the blade is in operation as a rotating element in the turbine.

STATEMENT OF THE DISCLOSURE One feature of the disclosure is a blade insert that is separately formed and is then positioned within the main blade the insert having a root portion cooperating with the root of the main blade. Another feature is the formation of blade attaching serrations on both root portions so that the insert is supported directly from the disk on which the row of blades is mounted.

Another feature is a method for forming the insert to produce a hollow insert having passages appropriately located therein for directing the flow of cooling air onto and across the inner wall surface of the main blade. Another feature is a process for producing and assembling the two piece blade and insert such that the desired configuration of the insert may be manufactured prior to assembly within the main blade.

According to the disclosure an insert for turbine blade is formed from a tube one end of which is enlarged by metal gathering to form a root portion after which the root portion is forged to a substantially rectangular configuration and the remainder of the tube is formed to a hollow air flow configuration with transverse openings located therein for directing the flow of air through said tube in the appropriate direction to engage proper wall surfaces of the surrounding blade and also forming blade attachment serrations on opposite surfaces of the root portion. The blade insert is assembled by inserting it through a notch formed in the root portion of the main hollow blade and the serrations on the insert will be in alignment with the serrations on the main blade root so that both insert and the main blade are supported from the serrations in the grooves in the periphery of the disk, in which the row of blades is mounted.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view of a tube before the start of the forming operation.

FIG. 2 is a view of the tube of FIG. I with the material that went into the tube metal gathered.

FIG. 3 is a view showing the step of finishing the metal gathered portion to the selected dimension internally and externally thereof.

FIG. 4 is an end view showing the forging step.

FIG. 5 shows the steps of thinning the tube and forging this end of the tube so that the metal gathered portion becomes substantially rectangular.

FIG. 6 is an end view of the root of FIG. 5.

FIG. 7 is a view similar to the preceeding figures showing the remainder of the tube formed into an airfoil shape for insertion within the main turbine blade.

FIG. 8 is a view showing the insert in position within the hollow main blade.

FIG. 9 is a sectional view along the line 9-9 of FIG. 8 showing the insert with a row of holes therein these holes having been provided prior to the assembly of the insert with the main blade.

DESCRIPTION OF THE PREFERRED EMBODIMENT The manufacture of the insert for the turbine blade is begun with a tube of the appropriate diameter and of the appropriate alloy to withstand the temperatures at which theblade will operate and with the tube longer than the finished blade by a substantial amount as shown in FIG. 1 where the tube is materially longer than the finished insert 4 of FIG. 7.

As the first step in forming the insert, the material of the tube at the bottom end thereof is metal gathered to form an enlargement 6. This enlargedportion 6' is hollow, since the finished blade has a central passage extending through the root portion which is formed from the metal gathered enlargement 6.

The next step after the metal gathering operation is to machine the outside of the metal gathered portion 6 to a sleeve shape 8 the inner and outer surfaces ofwould prevent the appropriate and accurate forming of the device.

After the sleeve 8 is formed and this is generally done A by machining both inside and outside surfaces, the portion of the tube that is later shaped to an airfoil configuration is chemically milled on the outside diameter for reducing the thickness thereof to the minimum thickness as can withstand the loadingon the insert when the device is in use. The chemical milling is represented in FIG. 5 where the chemical milling is from the top of the tube down to a shoulder 12 as shown and the thickness of the tube is represented in this figure as being thinner than the thickness in FIGS. 2 and-3.

The next step is to hot forge the root portion into a substantially elliptical or oval shape 14, FIG. 4 to make the root more nearly the shape of the finished root configuration. The elliptical or oval shapeis represented in FIG. 4 which shows the end of the blade rootwith the substantially elliptical shape and the central opening therein.

The next stepis to machine the root into a rectangularconfiguration with the end surfaces 16 parallel to one another and the side surfaces 18, FIG. 6 tapering toward each other to conform to the finished shape of the root.

The next step is to form the airfoil portion of the insert to a substantially airfoil configuration as shown in FIG. 9, this forming being accomplished by positioning the tubing between appropriate dies and. shaping the tube only in the thinner portions above the shoulder 12 at which point the tubing becomes thicker.

One of the particular problems in making an insert of this type is the formation of holes positioned laterally in the airfoil portion and through which cooling air is directed from within the insert against the inside wall surface of the main blade. Since the insert is a separate element, these holes 20, FIG. 7 may readily be formed in the tubing either before or after the tube is formed into the airfoil configuration. In any event, with the insert outside of and separate from the main blade, it is obvious that these openings may easily be machined at the appropriate location. For example, as shown, the openings 20 are preferably located so they direct cooling air against the inner surface of the main blade at the leading edge thereof. Obviously, other appropriate cooling passages as indicated at 22, FIG. 9 may be provided.

With the insert now in the configuration of FIG. 7, it may be inserted within the main blade 24 as shown in FIG. 8. As best shown in FIG. 8, the airfoil portion of the tube is no longer in chord length than the length of the root portion of the insert or the length of a notch 26 in the main blade root so that the insert may be inserted as a unit through the notch 26. This notch is provided in the root portion of the main blade and extends transversely therethrough. The insert is inserted upwardly within the main blade into the position shown in FIG. 8 where the root portion 18 of the insert is in lateral alignment with the root portions 28 of the main blade, these portions 28 being located at opposite ends of the root portion 18 of the insert.

Either prior to positioning the insert within the main blade, or subsequent thereto the insert has serrations 30 formed thereof in alignment with similar serrations 32 on the root portions 28 of the main blade so that when the assembled blade structure is positioned within a supporting disk the serrations 30 and 32 will all engage with the cooperating serrations in the notches in the disk which serve to support the blades in position.

The assembled structure of FIGS. 8 and 9 has the insert positioned within and spaced from the surrounding blade 24 over the entire airfoil portion thereof and once assembled the cooling passages 20 and 22 will be appropriately located to cool effectively those portions of the main blade that require a cooling action in order to withstand the high temperature of the turbine in which the blades are positioned. Obviously, in order that cooling air may flow out the passages 20 and 22 a suitable cap 34, FIG. 7 is attached to the tip end of the insert at some point in the manufacturing process after the airfoil shape has been produced in the insert.

It will be understood that in making a blade insert as described, since the article started with is a tube, it is readily possible to retain the hollow construction throughout the several steps in the process so that there is always an opening through the root portion of the insert without the need for separately producing this passage at some point in the manufacture of the article. Having established the area of the central passage as a function of the amount of cooling air necessary for flow through the openings 20 and 22, it is possible in maching the root portion when it is in the form of an enlargment as in FIG. 2, produce in that inside surface of the machined enlargement 8 a dimension such that when the blade is finished the cross sectional area will be adequate to permit the flow of the desired amount of cooling air.

I claim:

1. In the manufacture of a hollow cooled turbine blade having a blade root and an airfoil portion projecting therefrom and an insert therein, the steps of making a main blade with a hollow airfoil portion and an integral root portion at one end thereof with a transverse notch therein communicating from the base of the root into the airfoil portion and with attachment serrations on opposite surfaces of the root portion,

forming an insert with a hollow airfoil portion and with a root portion to fit in the transverse notch in the main blade,

forming air flow passages laterally through the wall of the hollow airfoil portion of the insert, and assembling the insert in the main blade by sliding the airfoil portion of the main blade through the transverse notch and into the main blade, and positioning said insert with the root portion of the insert fitting in said transverse groove.

2. The process of claim 1 with the added step of forming serrations on the insert root to align with the serrations on the main root.

3. The process of claim 1 with the added steps of forming the root portion on the insert to conform to the configuration of the transverse notch in the root portion of the main blade and forming the airfoil portion of the insert of such a dimension that it will pass through the transverse notch in said root portion in assembly of the insert within the main blade. 

1. In the manufacture of a hollow cooled turbine blade having a blade root and an airfoil portion projecting therefrom and an insert therein, the steps of making a main blade with a hollow airfoil portion and an integral root portion at one end thereof with a transverse notch therein communicating from the base of the root into the airfoil portion and with attachment serrations on opposite surfaces of the root portion, forming an insert with a hollow airfoil portion and with a root portion to fit in the transverse notch in the main blade, forming air flow passages laterally through the wall of the hollow airfoil portion of the insert, and assembling the insert in the main blade by sliding the airfoil portion of the maIn blade through the transverse notch and into the main blade, and positioning said insert with the root portion of the insert fitting in said transverse groove.
 2. The process of claim 1 with the added step of forming serrations on the insert root to align with the serrations on the main root.
 3. The process of claim 1 with the added steps of forming the root portion on the insert to conform to the configuration of the transverse notch in the root portion of the main blade and forming the airfoil portion of the insert of such a dimension that it will pass through the transverse notch in said root portion in assembly of the insert within the main blade. 